Hi OP,
We have two girls there. It's a lovely school and the girls are great, there's also a strong parent community, which you'll be welcomed into. With the normal 'new girls and new parents' social events before your DD starts and you'll obviously join the WhatsApp groups, where loads of 'parent coffee' events, after school socials etc. are advertised for you guys to go to if you want.
The school have always taken half their intake from outside for year 7 at the 11+. In fact one of my DDs was an 'external'. They are very, very used to it, and know exactly what to do to make girls feel welcome, integrated and part of the community. There's loads of social events and sports, team builds, preseason training, a year 7 trip really early on, etc. So that everyone mingles.
The prep school always has girls joining in all year groups too, so all the existing girls are very much used to having new classmates from outside and they are 'brought up' on Mrs Fry's (the prep head) values of being kind, helpful and welcoming to all. So, simply put, it's not a very cliquey place to begin with, but your DD will settle in well anyway.
Clubs, extracurricular and sport is open to everyone and its not (apart from the top end teams) related to performance. If your DD wants to do drama, sport, rowing, computing, lego club, debating, e-sports, then she can! She'll also meet like minded new friends at these clubs, it's a great and quick way they help to integrate new girls.
I'm not sure about costs on rowing, but we've never paid for anything the girls do (apart from an external music teacher for one of them). If there is a rowing cost, its won't be much I'm sure and will likely be to just cover any special events, dame with for example, a drama trip to a theatre, where you might just pay the cost of the ticket.
There are trips, lots and lots of them! But since Mr Boyd has been there, there as been a massive focus on making sure there's something for everyone, in terms of both interest and cost. So girls who don't want to go on a ski trip can have just as much fun on a much cheaper trip (like a battlefields trip to northern France or a UK based trip) or activity with lots of like minded girls.
Generally Tormead is the cheapest school in the area for fees, even with the VAT, and you get a lot for what you pay for, so we think its good value for money. When we had parent town hall meetings about VAT being applied, we saw various graphs comparing costs against academic results and we were very satisfied that we were still getting the best deal I'm the area despite being robbed blind by Racheal Reeves!
Not sure if my waffle helps, I post on here quite often about various topics and can never keep it short! Hahaha
Ps. If you what an offline conversation just drop me a PM!